Improvement in Structure and Visible Light Catalytic Performance of g-C3N4 Fabricated at a Higher Temperature

Abstract

A highly-efficient graphitic carbon nitride (g-C3N4) photocatalyst for visible light photodegradation of rhodamine B (RhB) and methyl orange (MO) simulating dyeing wastewater was synthesized by the thermal polycondensation of melamine. The photocatalysts were characterized by TG-DTG-DSC, XRD, EA, XPS, FT-IR, SEM, TEM, BET, PL and UV-vis DRS. The results showed that the photocatalytic performance of g-C3N4 at a higher calcination temperature was significantly enhanced, and its photocatalytic activities for the photodegradation of RhB and MO were remarkably improved by 64.91% and 41.83%, respectively, which was mainly attributed to the satisfactory crystallinity, stable graphene-like structure, large surface area, and excellent optical properties. It was found that •O2− radicals and •OH radicals were the main active species for the photodegradation process by the free radicals trapping experiments and ESR analysis. The photodegradation mechanism of g-C3N4 was proposed predicated using the characterization results.

Single-Step Synthesis of Graphitic Carbon Nitride Nanomaterials by Directly Calcining the Mixture of Urea and Thiourea: Application for Rhodamine B (RhB) Dye Degradation

“…As a result, an increase in peak sharpness indicated a higher degree of crystallinity of a photocatalyst [ 51 ]. Therefore, a higher degree of crystallinity of the photocatalyst accelerated the transfer of charge carriers to the surface, thereby inhibiting photoinduced electron-hole recombination by promoting the separation of charge carriers [ 19 ].…”

“…The majority of photocatalysis research has used xenon lamps [ 19 , 20 ], halogen lamps [ 21 ], UV lamps [ 22 ], and mercury vapor lamps [ 23 ] as the light source, which has some advantages but is dangerous, has a short lifetime, overheats, is expensive and difficult to handle [ 24 ]. Recently, in the field of photocatalysis technology, less toxic, longer life, less expensive, and environmentally friendly light-emitting diodes have been employed as visible light sources for organic pollutant degradation [ 24 , 25 ].…”

“…Therefore, researchers have made numerous attempts to overcome the limitations of pristine g-C 3 N 4 , such as elemental doping [ 27 , 34 , 35 , 36 ], controlling morphology [ 37 ], and constructing g-C 3 N 4 -based heterojunctions [ 38 , 39 , 40 ]. Moreover, recently various studies have been conducted on g-C 3 N 4 for photocatalytic elimination of pollutants [ 19 , 24 , 41 ], photoreduction of carbon dioxide [ 42 , 43 , 44 ], water splitting for hydrogen production [ 28 , 45 ], and so on.…”

“…Similarly, calcination temperature control is one of the most common reaction parameters affecting the performance of the g-C 3 N 4 photocatalyst. As a result, the synthesis of g-C 3 N 4 by varying calcination temperature allows improvements in the surface area, crystallinity, extended absorption range of visible light, and overall enhanced photocatalytic activity [ 19 , 20 , 32 ]. Therefore, some recent studies have been carried out on the influence of calcination temperature on g-C 3 N 4 photocatalytic performance.…”

“…Moreover, Ke et al synthesized g-C 3 N 4 for the decomposition of rhodamine B (RhB) and methyl orange (MO) via thermal polycondensation of melamine at different calcination temperatures ranging from 450–700 °C. The g-C 3 N 4 prepared at a calcination temperature of 700 °C revealed robust photocatalytic activity and stability against RhB and MO decomposition [ 19 ]. In addition, according to a review of the published literature in the field of visible-light-driven photocatalysis, the calcination temperatures for the fabrication of g-C 3 N 4 using urea and thiourea were generally considered to be in the range of 520–550 °C and 450–650 °C, respectively [ 48 ].…”